Browsing by Author "Zhang, Kailun"

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    Mechanism of Silica Reduction by MgO during Warm Lime Softening of SAGD Produced Water
    (2020-09-24) Zhang, Kailun; Qingye, Lu; Dong, Mingzhe; Gates, Ian D.
    Magnesia (MgO) is usually used to treat produced water from steam-assisted gravity drainage (SAGD)-based oil recovery as a silica reduction agent in a warm lime softener (WLS). This work aims to understand MgO slaking chemistry and silica reduction mechanism by slaked and non-slaked MgO. The impact of common particles in SAGD produced water including calcium, magnesium, bicarbonate, humic acid, and clay on silica reduction by MgO in the WLS was also investigated. MgO slaking process was studied by monitoring the zeta potential and pH of MgO slurries with three initial slurry densities in water (0.5%, 1% and 2%) over time. Silica reduction by slaked and non-slaked MgO was studied at SAGD WLS operating conditions (pH, temperature and contact time). Characterizations such as SEM-EDX, XRD, FTIR, TGA and XPS were performed to help understand the silica reduction mechanisms. The interactions of MgO with various particles were studied by measuring the zeta potential of the mixtures at 65oC. The zeta potential of MgO suspension depends on temperature, hydration time, and MgO slurry density with the initial zeta potential varying from +10 to +15 mV. Additionally, the influence of different particles on silica reduction by MgO at WLS operating temperature of 85oC was evaluated. Thermodynamic modeling was performed using Visual MINTEQ to understand the potential reactions during silica reduction. The understanding of silica reduction mechanism by MgO in the WLS including the impact of MgO hydration is essential for guiding onsite chemical dosages and operational process control.